Back in 2010, we said:

...as well as a 300-volt nickel-metal-hydride battery pack. In all, the hybrid system is rated at 332 horsepower and 367 pound-feet of torque, which pushes EPA fuel economy to 21/22 mpg for two-wheel-drive models, and 20/20 mpg with 4WD. Driving the Hybrid is remarkably similar to driving the Silverado with the 5.3-liter V-8 engine--that is, except for the almost absurd smoothness and quietness as the Silverado runs up to 27 mph on battery power alone. The Silverado Hybrid's brakes are powerful and recapture energy to charge the batteries. Even saddled with more curb weight... Read More